The service life of some wells can be decades long. Many such wells have downhole devices that are remotely actuated. In some applications the actuator assemblies must be located downhole. Some downhole devices require fairly precise movements for proper control of the downhole operation. For example, valves have a variable orifice feature that regulates the amount of the flow that is delivered per unit time.
Over long periods of use, actuator systems that use resilient seals can experience seal failure that allows the downhole fluids to reach the precision components of the actuator and an ultimate failure of the actuator. This requires an expensive overhaul that causes lost production or at least delayed production and the associated expense of the workover to get the broken actuation equipment removed from the wellbore so it can be either repaired or replaced.
A better way that is offered by the present invention is to encase the actuation equipment in a manner to seal it from well fluids to ensure its long term trouble free operation. The operation of the actuation equipment within the sealed enclosure is transferred through a sealed transfer device through the wall of the sealed enclosure to the device or tool on the outside whose movement is needed to control the downhole function. In a preferred embodiment the actuator moves a bellows in the isolated enclosure that triggers a response in a slave bellows that is operably connected to the downhole tool being controlled. In between the master and slave bellows there is a body that is sealed to an opening in the fluid enclosure preferably by welding. In a preferred application the ultimate controlled element moved by this system is one or more variable orifice valves. Position sensors can be optionally used as one form of feedback for calibration of the device. The master/slave bellows can be optionally guided in their movements and the thermal effects within the sealed enclosure can be compensated by a discrete relief device, such as another bellows.
Bellows have been used to transfer actuator movement to a remote location all within a nuclear reactor as shown in U.S. Pat. No. 5,369,675. Other patents and applications in the general field of transfer of force through hydraulic systems are: U.S. Pat. Nos. 3,208,541; 3,392,795; 3,570,612; 3,606,297; 3,949,821; 4,111,271; 4,161,224; 4,361,195; 4,593,771; 4,658,917; 4,865,125; 5,007,479; 5,033,557; 5,058,673; 5,070,940; 5,287,921; 5,931,242; 7,025,130 and 7,185,699. The following other patents are also relevant: UA 19496; EP 1473435 and WO 03033859.
Those skilled in the art will appreciate that there are a variety of downhole applications that the present invention can be used and a better understanding of the extent of the invention can be better appreciated from a review of the description of the preferred embodiment and the associated FIGURE while recognizing that the full scope of the invention is determined by the appended claims.